278 Transactions. 



dorsally, and a second later the perfect fly is outside and standing upon 

 it, The wings begin to expand with a kind of uncurling movement, 

 ' gradually extending outwards and up till they are held straight above the 

 abdomen, their upper surfaces turned inward and together ; then with 

 a sudden relaxing motion they fall to their natural position across and 

 on either side of the dorsum. The whole operation of emerging and dry- 

 ing the wings takes less than a minute. The fly is rather a sluggish insect, 

 but quick of flight, and is often to be met with indoors. It is, however, 

 harmless to man and beast, and probably destroys a great amount of 

 unhealthy and decaying matter. 



Hob. — Wellington (Hudson), Wanganui (M. N. W.) ; probably to be 

 found in most parts of New Zealand. 



" P. phalaenoides, Christchurch (Hutton), Auckland (Suter) ; intro- 

 duced from Europe." 



No. 6. Syrphus ropalus Walk. 



Syrphus ropalus Walker, Cat, Dipt, Brit, Mus.. p. 593 (1849): 

 Hutton, Cat, Dipt. N.Z., p. 44: Trans. N.Z. Inst,, vol. 33, 

 p. 41. 



The family to which this fly belongs is a very common one — Syrphide, 

 or hover-flies — and of great value from an economic point of view. As 

 far as can be .seen, nothing has been published concerning the habits and 

 life-history of the present species. The egg stage is. unfortunately, still 

 unknown, but may not differ very much from that of other flies of the 

 same family, several of which are quite well known. 



The larva is of a light-green colour, and attains a length of about 4 in. 

 when full grown, and is greatly attenuated towards the head ; it is soft- 

 skinned and moist ; the skin transparent, displaying clearly the whole 

 alimentary system. Specimens were invariably found in the narrow spaces 

 between the outer leaves of the heart of the cabbage-tree (Cordyline aus- 

 tralis). The larva dislikes the light, and, when exposed, quickly makes off 

 into the dark crevices between the leaves. The mode of progression is 

 the same as in all other arboreal larvae of this family. It is a mystery how 

 the blind larva finds his way, and is able to hunt out his prey, which in the 

 present cases consists of the larvae of a Lepidopteron (Venusia verriculata) 

 which also breed in the cabbage-tree. The reader is referred to No. 3 of 

 this series of contributions for full notes on the breeding of this moth (Trans. 

 N.Z. Inst., vol. 47, p. 268). It seems hardly likely that the prey is captured 

 fortuitously. When a caterpillar is discovered, the larva, with a lightning 

 toss of the head, plunges his beak into its body. The caterpillar will not 

 submit quietly to this, but writhes and twists and twirls its body about, 

 and even frequently attempts to bite its antagonist, sometimes in this way 

 forcing the maggot to beat a hasty retreat. It is wonderful to see the way 

 in which the larva sticks to his prey in spite of all the heaving convulsions ; 

 this he manages by ejecting a quantity of sticky mucus which practically 

 cements him to the caterpillar. In the meantime, while the prey is still 

 living, the maggot is rooting luxuriously amid its entrails, till nothing but 

 the empty skin remains. The larval stage exists some length of time, pro- 

 bably several months. They feed on the larvae of Venusia verriculata, 

 but in captivity also took readily to the larvae of another moth, Tortrix 

 postvittana, which also feed in the head of the cabbage-tree, curling the tips 

 of the leaves. 



